1. Field of the Invention
The present invention is directed to reducing noise in a motor vehicle, and in particular, a new throttle plate and method of design to reduce air rush noise generated as air moves past a partially opened throttle plate into the vehicle intake manifold.
2. Background and Description of the Prior Art
Electronic fuel injection systems in vehicles have replaced carburetor systems in an effort to reduce engine emissions and increase fuel efficiency. When the driver depresses the gas pedal on a fuel injected vehicle, the throttle valve opens inside the throttle body, letting in more air. The air travels through the engine intake manifold, where it mixes with fuel from the fuel injectors and enters the engine cylinders to increase power to the vehicle. When the air rushes through the throttle body into the manifold, increased turbulent air flow is created, which can make significant noise.
Noise reduction has been a major goal of automakers in motor vehicles for the past several years. With global competition in vehicle sales, automakers often try to differentiate their vehicles from the competition by their xe2x80x9csound characteristics.xe2x80x9d As major vehicle noises are reduced, other long-standing background noises must be addressed. Air rush noise through the intake system when the throttle plate is opened is one of those noises.
High frequency flow noise can be created when a butterfly valve (the throttle plate) is opened from the fully closed position to some partially open position. Due to its inherent lower material density, this can be especially troublesome in composite-based air intake systems. The convergence of turbulent air streams through the openings created on either side of the throttle plate creates what is described as a xe2x80x98whooshxe2x80x99 noise by customers. The condition can exist at xe2x80x98tip-inxe2x80x99 (the rapid opening of the fully closed throttle plate) or at a steady state, part-throttle condition.
Several designs currently exist to reduce the air rush noise in a vehicle. One method is seen in U.S. Pat. No. 5,722,357 issued to Choi. This patent describes a gasket-like piece that is added between the throttle body and the manifold to diffuse the air flow downstream from the throttle plate. Vanes project from the interior of the circular opening to diffuse the air flow and reduce the noise. Since the vanes are not located at the source of noise, this method is less effective at reducing the noise. The addition of these protrusions can also act to partially impede the flow resulting in an increased pressure drop leading to a minor loss of power when the throttle plate is fully open. This method, however, requires an extra component to be installed on every vehicle. This is not cost-effective for mass production.
The use of protrusions downstream of the throttle plate is also discussed in U.S. Pat. No. 5,970,963 issued to Nakase et al. Several different types of protrusions from the downstream side of the throttle valve are discussed. These protrusions severely complicate the die cast tooling necessary to make the throttle body. Slides will need to be added to the die cast tool and extra machining of the casting will be necessary. This adds cost to the component and reduces production volume. The addition of these protrusions can also act to partially impede the flow resulting in an increased pressure drop further leading to a minor loss of power when the throttle plate is fully open.
Adding protrusions to the throttle plate to reduce the air rush noise has been addressed in U.S. Pat. No. 5,881,995 issued to Tse et al. and U.S. Pat. No. 5,465,756 issued to Royalty et al. Both patents describe noise reduction components added to the throttle plate to attenuate the noise. The fins on the designs, however, are of a fixed geometry to the throttle plate. While these will reduce some of the air rush noise, they may not eliminate it in all vehicle models. Manifolds and throttle bodies vary in shape, which changes the fluid dynamics and noise in the vehicles necessitating an adaptable throttle plate design. The subject matter of the above referenced patents may also have reduced power when the throttle plate is fully open due to the pressure drop caused by protrusions of these types. There still exists a need to optimize these protrusions. No optimization techniques are discussed.
The need thus still exists for a flexible throttle plate design that reduces the air rush noise across vehicle models. There needs to be a method to accomplish the noise reduction while not causing a power loss when the throttle plate is fully open. There also needs to be a method of optimizing and customizing the design to reduce the air rush noise in each individual vehicle to accommodate the different manifold and throttle body designs.
In accordance with the present invention, these and other objects are accomplished by providing an apparatus and a method for reducing the air rush noise in a variety of motor vehicles when the throttle plate is open. This reduction is for throttle plates that are gradually opened, held in a partially-open position or are rapidly opened.
On a vehicle, the throttle plate opens when the engine needs to deliver more power. The air flow over the throttle plate inside the throttle bore can cause increased turbulence and vorticies. Fins added to the throttle plate can prevent the vorticies from being generated and act to straighten the flow, thus mitigating the turbulence in the flow downstream of the plate. The fins delay convergence of the turbulent air to a point further downstream when the energy has been dissipated. This, in turn, mitigates the source of the noise. With the fins attached to one or both sides of the throttle plate, the designer has the ability to tune the acoustical response as well as the restriction imposed by the fins minimizing the effect on the engine""s power output. The fins may be of constant width and spaced consistently across the throttle plate, or the spacing and width may vary.
The present invention uses fins in one or more orientations on the throttle plate to manage the flow of the air through the throttle bore to the manifold to mitigate the source of the noise. The throttle bore may be cylindrical, oval, elliptical, or a similar shape. A variety of computational fluid dynamics and other computer aided engineering methods, along with bench testing, can be used to simulate the flow of the air through the specific throttle body/manifold design to simulate the air flow and optimize the design of the fins of the throttle plate. This optimization depends upon many factors including the duct section geometry of the induction system, the airflow rate, and customer design specifications for pressure drop and radiated sound levels. The fins can be fabricated of various materials such as composite plastics or die cast aluminum. The fins can be attached to the throttle plate by various methods such as a mechanical joint, adhesive or welding. The fins could also be integrated into the plate as a one-piece design.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.